The Science of Self-Control

When hunger strikes, do you reach for celery or a candy bar? How well you stick to your diet could depend on the activity of a small region in your forebrain, according to a new study on self-control. The research could open doors to better understanding destructive behaviors such as overeating, drinking, and smoking.

Behavioral researchers have long known that self-control is an important component of decision-making. But less is understood about the brain regions involved. Several areas in the forebrain show activity when a person makes tough choices, yet scientists disagree on how these regions work together. How, for example, does the brain weigh the short-term sugar rush of a chocolate bar against the long-term health benefits of a salad?

Now, researchers from the California Institute of Technology in Pasadena say they have the answer. The scientists recruited 37 dieters who had been successful in losing or maintaining weight. The volunteers fasted for 3 hours and then entered a functional magnetic resonance imaging machine (fMRI), which measures brain activity. While inside, they viewed pictures of 50 different foods and rated each on a five-point scale for how healthy and tasty they considered it to be.

The researchers then picked a food the dieter had rated neutral on both scales and asked the person to choose between that food and each of the 49 other options. Although all of the participants labeled themselves "dieters," about half threw self-control to the wind and went for the tastier treats, while the other half chose the healthier options.

The difference seems linked to a region of the brain called the dorsolateral prefrontal cortex. This region, previously associated with learning and memory, lit up on fMRI only when volunteers picked a healthy food over something more tempting. In other words, the dorsolateral area seems to act like the neural version of a concerned mother, telling us to eat our peas before we reach for dessert. "One of the differences between people who are good at using self-control and those who are poor at self-control might be the ability to" activate the dorsolateral prefrontal cortex, says Todd Hare, a Caltech neuroscientist and lead author of the paper, published today in Science (p. 646).

Hare has "got his finger on or right next to the part of the brain that controls how farsighted or healthy a person is going to be," says New York University neuroeconomist Paul Glimcher. The research could lead to treatments for behavioral issues such as overeating or drug use by showing researchers where in the brain those problems originate, he says: "I am really optimistic that we are at the beginning of a new frontier."